1. Technical Field
The present invention relates to a hydraulic fluid supply device capable of supplying hydraulic fluid, and an electric actuator adopting such a hydraulic fluid supply device.
2. Background Art
There have been known an electric actuator such as one described in Japanese Unexamined Patent Publication No. 54604/2002 (Tokukai 2002-54604; hereinafter, Patent Citation 1), which adopts a hydraulic fluid supply device capable of supplying hydraulic fluid. This electric actuator has an electric motor, a pump which outputs oil according to the rotation of the electric motor, a cylinder into which the oil output from the pump is input, a controller which controls the rotation of the electric motor according to the motion of the cylinder, and a backup valve which circulates the oil output from the pump in the cylinder. When the pressure of oil input to the cylinder equals or surpasses a predetermined pressure, the backup valve stops circulation of the oil output from the pump. Since the backup valve provides a support for a force applied to the cylinder in the above structure, there is no need for supplying oil from the pump to the cylinder.
However, in the electric actuator of Patent Citation 1, the electric motor needs to be driven to output a high torque when supplying high pressure oil from the pump. In other words, a high current needs to be supplied to the electric motor which drives the pump. This increases the amount of heat generated by the electric motor, the controller of the electric motor, or the like. This generated heat, if causing an increase in the temperature of the electric motor or the like, may yield an adverse effect such as a problem in driving and controlling the electric actuator, thus deteriorating the reliability of the electric actuator. Further, the need of supplying a high current in the electric motor raises concern about an increase in the power consumption of the electric actuator. A conceivable approach to solve this problem is to ensure a sufficient heat dissipation area by increasing the surficial area of the electric actuator. This approach however causes a problem of an increase in the volume and weight of the electric actuator.
The present invention is made in view of the above circumstances, and it is an object of the present invention to provide a hydraulic fluid supply device capable of supplying a high pressure hydraulic fluid with a low current, and an electric actuator capable of outputting a high performance with a low current.